From a51d0555e1a2c4dfaa88bc9155f8873bc8913f06 Mon Sep 17 00:00:00 2001
From: Vincent Breitmoser <look@my.amazin.horse>
Date: Mon, 30 Oct 2017 22:57:13 +0100
Subject: [PATCH] Retain RSA public exponent length when setting key attributes
 in putKey operation

Similar to the previous commit, openpgp applet implementations differ in
regards to the public exponent length. As of this writing:
- The SmartPGP applet requires an 11 bit public exponent size
- The Gnuk token requires a 32 bit public exponent size

For this reason, we simply set the public exponent size to the one
previously set in the key attribute info. With this commit, the only
variable that can actually change for an RSA key is its modulus size.
---
 .../securitytoken/SecurityTokenUtils.java     | 36 ++++++++++---------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/SecurityTokenUtils.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/SecurityTokenUtils.java
index 35f12a317..0a87fa01a 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/SecurityTokenUtils.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/SecurityTokenUtils.java
@@ -22,6 +22,7 @@ import org.bouncycastle.util.Arrays;
 import org.bouncycastle.util.encoders.Hex;
 import org.sufficientlysecure.keychain.pgp.CanonicalizedSecretKey;
 import org.sufficientlysecure.keychain.pgp.exception.PgpGeneralException;
+import org.sufficientlysecure.keychain.securitytoken.RSAKeyFormat.RSAAlgorithmFormat;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -33,24 +34,12 @@ import java.security.interfaces.RSAPrivateCrtKey;
 
 class SecurityTokenUtils {
     static byte[] attributesFromSecretKey(KeyType slot, CanonicalizedSecretKey secretKey, KeyFormat formatForKeyType)
-            throws IOException, PgpGeneralException {
+            throws IOException {
         if (secretKey.isRSA()) {
-            final int mModulusLength = secretKey.getBitStrength();
-            final int mExponentLength = secretKey.getSecurityTokenRSASecretKey().getPublicExponent().bitLength();
-            final byte[] attrs = new byte[6];
-            int i = 0;
-
-            attrs[i++] = (byte) 0x01;
-            attrs[i++] = (byte) ((mModulusLength >> 8) & 0xff);
-            attrs[i++] = (byte) (mModulusLength & 0xff);
-            attrs[i++] = (byte) ((mExponentLength >> 8) & 0xff);
-            attrs[i++] = (byte) (mExponentLength & 0xff);
-            attrs[i] = ((RSAKeyFormat) formatForKeyType).getAlgorithmFormat().getValue();
-
-            return attrs;
+            return attributesForRsaKey(secretKey.getBitStrength(), (RSAKeyFormat) formatForKeyType);
         } else if (secretKey.isEC()) {
-            final byte[] oid = new ASN1ObjectIdentifier(secretKey.getCurveOid()).getEncoded();
-            final byte[] attrs = new byte[1 + (oid.length - 2) + 1];
+            byte[] oid = new ASN1ObjectIdentifier(secretKey.getCurveOid()).getEncoded();
+            byte[] attrs = new byte[1 + (oid.length - 2) + 1];
 
             if (slot.equals(KeyType.SIGN))
                 attrs[0] = ECKeyFormat.ECAlgorithmFormat.ECDSA_WITH_PUBKEY.getValue();
@@ -68,6 +57,21 @@ class SecurityTokenUtils {
         }
     }
 
+    private static byte[] attributesForRsaKey(int modulusLength, RSAKeyFormat formatForKeyType) {
+        RSAAlgorithmFormat algorithmFormat = formatForKeyType.getAlgorithmFormat();
+        int exponentLength = formatForKeyType.getExponentLength();
+
+        int i = 0;
+        byte[] attrs = new byte[6];
+        attrs[i++] = (byte) 0x01;
+        attrs[i++] = (byte) ((modulusLength >> 8) & 0xff);
+        attrs[i++] = (byte) (modulusLength & 0xff);
+        attrs[i++] = (byte) ((exponentLength >> 8) & 0xff);
+        attrs[i++] = (byte) (exponentLength & 0xff);
+        attrs[i] = algorithmFormat.getValue();
+
+        return attrs;
+    }
 
     static byte[] createRSAPrivKeyTemplate(RSAPrivateCrtKey secretKey, KeyType slot,
             RSAKeyFormat format) throws IOException {